Modular solar panels with heat exchange &amp; methods of making thereof

ABSTRACT

A photovoltaic module with photovoltaic cell and a heat sink. The heat sink is attached on a side of the cell opposite to the light-receiving side of the photovoltaic cell. The heat sink can remove heat caused by light absorbed by the photovoltaic cell but not converted to electricity as well as heat generated by resistance to high current passing through electrodes of the photovoltaic cell. A photovoltaic module formed of such cells can exhibit greater energy conversion efficiency as a result of the ability to dissipate the heat. A method of making a photovoltaic module involves e.g. laminating a heat sink to a photovoltaic cell.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit of U.S. Provisional ApplicationNo. 60/874,313, entitled “Modular Solar Roof Tiles and Solar Panels WithHeat Exchange” filed Dec. 11, 2006, which is incorporated by referencein its entirety herein as if it was put forth in full below.

BACKGROUND OF THE INVENTION

Solar energy is a renewable energy source that has gained significantworldwide popularity due to the recognized limitations of fossil fuelsand safety concerns of nuclear fuels. The photovoltaic (PV) solar energydemand has grown at least 25% per annum over the past 15 years.Worldwide photovoltaic installations increased by 1460 MW (Megawatt) in2005, up from 1,086 MW installed during the previous year (representinga 34% yearly increase) and compared to 21 MW in 1985.

Most growth in the field of solar energy has focused on solar modulesfixed on top of an existing roof. Rooftops provide direct exposure ofsolar radiation to a solar cell and structural support for photovoltaicdevices. Despite increased growth, the widespread use of conventionalroof-mounted solar modules has been limited by their difficulty and costof installation, lack of aesthetic appeal, and especially their lowconversion efficiency.

Most conventional roof-mounted solar modules are constructed largely ofglass enclosures designed to protect the fragile silicon solar cells.These modules are complex systems comprising separate mechanical andelectrical interconnections that are then mounted into existingrooftops, requiring significant installation time and skill. Availablemodules are also invasive in the aesthetics of homes and commercialbuildings, resulting in limited use. A few manufacturers have fabricatedmore aesthetically pleasing and less obstructive solutions, but thesystems are not price competitive largely due to installationdifficulties and poor total area efficiency. Lower module efficiencylevels are correlated to higher photovoltaic system costs because agreater module area is required for a given energy demand.

The efficiency of converting light into electricity for a typicalcrystalline-silicon roof-mounted solar cell is approximately 13%. Somesystems have seen efficiency increases (up to 18-20%) by modificationssuch as the use of anti-reflective glass on the cell surface to decreaseoptical reflection, use of textured glass on the cell surface toincrease light trapping, and the use of improved materials like thinfilm silicon or germanium alloy. Despite these improvements, solar cellconversion efficiency remains limited, in part, by high solar celltemperatures. The efficiency of a photovoltaic device decreases as thetemperature increases. Part of the energy radiated onto the cell isconverted to heat, which limits the electrical energy output and overallconversion efficiency of the cell. Fabrication of a system capable ofremoving heat from the photovoltaic cell would greatly increase totalefficiency.

There is significant interest in and need for a photovoltaic module thataddresses the above problems.

BRIEF SUMMARY OF THE INVENTION

Described herein are various solar modules that produce energy from thesun's radiation as well as various methods employed in fabrication ofthose solar modules. Some of the modules have increased efficiency inconverting solar energy to electricity. Some modules are aestheticallyattractive and well suited for installation over top of conventionalroofs.

In one instance, a method of fabricating a photovoltaic module has thesteps of: (a) placing a heat sink in a jig such that a lower surface ofsaid heat sink is in contact with said jig and an upper surface of saidheat sink is exposed; (b) placing a photovoltaic cell on the uppersurface; (c) joining the photovoltaic cell and the heat sink; and (d)removing the heat sink from the jig.

In another instance, the method includes lamination to attach the heatsink. In another instance, the method includes lamination of anintervening layer between the heat sink and the photovoltaic cell. Inanother instance, the intervening layer is a thermally conductivepolymer. In another instance, the polymer is an elastomer.

In another instance, the method includes decreasing the air pressurebetween the heat sink and the photovoltaic cell, preferably for between5 to 30 minutes. In another instance, the method includes increasing thetemperature between the heat sink and the photovoltaic cell, preferablyto between 125° C. and 175° C. In another instance, the method includesincreasing the temperature for between 5 to 30 minutes. In anotherinstance, the method includes increasing the pressure between the heatsink and the photovoltaic cell, preferably between 0.5 and 5atmospheres. In another instance, the method includes increasing thepressure between the heat sink and the photovoltaic cell between 5 to 30minutes.

In another instance, the method includes attaching a protective layer onthe photovoltaic cell. In another instance, the protective layer is aconformal coating.

In one instance, the method includes attaching a frame surrounding thephotovoltaic cell wherein the frame does not extend beyond said uppersurface, allowing unimpeded access of ambient air to the heat sink.

In another instance the heat sink of the method is constructed ofextruded aluminum. In another instance the heat sink is constructed of aconductive polymer. In another instance, the heat sink has a pluralityof fins substantially parallel to each other and said jig comprises aplurality of depressions complementary to said plurality of fins.

The present invention is better understood upon consideration of thedetailed description below in conjunction with the accompanying drawingsand claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a photovoltaic module with heat sinks.

FIG. 2 is a partial side view of a FIG. 1.

FIG. 3 is a bottom view of a heat sink.

FIG. 4A-1 is a cross-sectional view of an upper jig and a lower jig usedto construct a photovoltaic module.

FIG. 4A-2 is a bottom view of an upper jig.

FIG. 4B is the view shown in FIG. 4A-1 with a photovoltaic cell and aheat sink.

FIG. 4C is the view shown in FIG. 4B with an interface layer.

FIG. 4D illustrates the apparatus shown in FIG. 4C where the upper jigand lower jig are compressed.

FIG. 4E shows a side view of a photovoltaic module produced by thedescribed process.

DETAILED DESCRIPTION

The following description is presented to enable a person of ordinaryskill in the art to make and use the invention. Descriptions of specificmaterials, techniques, and applications are provided only as examples.Various modifications to the examples described herein will be readilyapparent to those of ordinary skill in the art, and the generalprinciples defined herein may be applied to other examples andapplications without departing from the spirit and scope of theinvention. Thus, the present invention is not intended to be limited tothe examples described and shown, but is to be accorded the scopeconsistent with the appended claims.

FIGS. 1 and 2 illustrate an example of a photovoltaic (PV) module 100 ofthe present invention. The photovoltaic module 100 comprises aphotovoltaic array of interconnected photovoltaic cells 110 positionedwithin a frame 120, which may be adapted to mount the module on afinished rooftop. Each photovoltaic cell is positioned within the frame120 to allow exposure of a cell's light-receiving surface to solarradiation.

Each photovoltaic cell 110 may be any currently used in the art ordeveloped in the future, such as a silicon-based wafer photovoltaiccell, a thin film photovoltaic cell, or a conductive polymer thatconverts photons to electricity. Such cells are well-known and includewafer-based cells formed on a monocrystalline silicon, poly- ormulticrystalline silicon, or ribbon silicon substrate. A thin-filmphotovoltaic cell may comprise amorphous silicon, poly-crystallinesilicon, nano-crystalline silicon, micro-crystalline silicon, cadmiumtelluride, copper indium selenide/sulfide (CIS), copper indium galliumselenide (CIGS), an organic semiconductor, or a light absorbing dye.

Each photovoltaic cell 110 may be of any shape (e.g. square,rectangular, hexagonal, octagonal, triangular, circular, or diamond) andlocated in or on a surface of a module. A photovoltaic cell in a moduleis one recessed within the module frame with essentially only the topsurface of the cell exposed to the light source. A photovoltaic cell ona module is one placed directly on top of the frame with essentiallyonly the bottom surface not exposed to the light source.

The electrical configurations between individual photovoltaic cells 110as well as the electrical connections between individual modules mayindependently be configured as series, parallel, or mixedseries-parallel as is well known in the art to achieve the desiredoperating current and voltage. For example, individual photovoltaiccells within a module are connected in series to increase the totaloperating voltage of the module. If the voltage produced by eachindividual photovoltaic cell within a module is sufficient, then thecells may be connected to adjacent cells in parallel to maintain voltageand increase current.

The photovoltaic module comprises one or more heat sinks 130 in thermalcommunication with the unexposed surface of the photovoltaic cells 110to dissipate the waste heat from the cells. As illustrated in FIG. 2,each heat sink may comprise a base 200 attached to the flat surface ofthe unexposed surface of the solar cells and a plurality of fins 210extending substantially perpendicular to a large surface of the base andsubstantially parallel to the long axis of each other. The base and finsmay be constructed separately and later joined, or constructed as oneunit from the same material source. The heat sink may be in directphysical contact with the solar cells or may have one or moreintervening layers. An example of an intervening layer is an interveningthermal interface layer 220, which can be made of any material used inthe art, such as thermally conductive grease or adhesive (e.g.conductive epoxy, silicone, or ceramic) or an intervening thermallyconductive polymer, such as a thermally conductive polymer availablefrom Cool Polymers, Inc. The intervening layer may be of any materialcommonly used in the art (e.g. ethyl-vinyl-acetate (EVA), polyester,Tedlar®, EPT). The thermal interface layer may be constructed ofmaterial that is both electrically isolative and thermally conductive.The thermal interface layer may be a thin layer of polymer that is notintrinsically thermally conductive but, due to its thinness, conductsheat at a sufficient rate that it is considered thermally conductive.Other layers may be present separately or in addition to an interveningthermal interface layer, such as one or more electrically insulatinglayers. The intervening layer may be in simultaneous contact with boththe solar cell(s) and the heat sink.

The heat sinks may be positioned substantially parallel or substantiallyperpendicular to the long axis of the module 100 and may span portionsof or the entire length or width of the module. Likewise, multiple heatsinks may be aligned in tandem, with or without intervening space, tospan the portions of or the entire length or width of the module, ifdesired. In one variation a heat sink has sufficient length to spangreater than ¾ of the length of the module. In another variation a heatsink has sufficient length to span greater than ¾ of the width of themodule. In some variations different heat sinks on the module will bepositioned substantially perpendicular to one another.

The base 200 and fins 210 of each heat sink can be independentlyconstructed of one or more thermally conductive materials, such asaluminum or aluminum alloy (e.g. 6063 aluminum alloy, 6061 aluminumalloy, and 6005 aluminum alloy), copper, graphite, or conductive polymer(such as conductive elastomer as available from, e.g. Cool Polymers,Inc.), and may be of any color, such as blue, black, gray, or brown.Dark colors may improve heat sink performance. A heat sink constructedof metal may be anodized or plated. Heat sinks may be constructed bycommon manufacturing techniques such as extrusion, casting, or injectionmolding, or may be constructed using a combination of manufacturingtechniques to construct hybrid heat sinks (e.g. aluminum fins moldedinto a conductive polymer base).

FIG. 2 illustrates dimensions of a heat sink 130. A base 200 may have athickness designated as t. Fins 210 may independently have a heightdesignated h, a center to center spacing designated as s, and a widthdesignated as w. The width w of any fin may be independently less than 1inch, or less than 0.75″, or less than 0.5″, or less than 0.3″, or lessthan 0.2″, or less than 0.15″, or less than 0.1″, or less than 0.05″, orless than 0.025″, or less than 0.01″, or less than 0.005″, or less than0.0025″, or less than 0.001″, or between 0.001″ and 0.25″, or between0.002″ and 0.1″, or between 0.005″ and 0.075″, or between 0.01″ and0.06″, or between 0.02″ and 0.05″, or 0.02″. The height h of any fin maybe independently greater than 0.1″, or greater than 0.25″, or greaterthan 0.5″, or greater than 0.75″, or greater than 1″, or greater than2″, or greater than 3.5″, or between 0.25″ and 7″, or between 0.5″ and6″, or between 0.75″ and 5″, or between 0.8″ and 2.5″, or between 0.9″and 2″, or between 0.9″ and 1.25″, or 1″. The center to center spacing sbetween fins may be independently between 0.05″ and 1″, or between0.075″ and 0.9″, or between 0.1″ and 0.8″, or between 0.2″ and 0.7″, orbetween 0.2″ and 0.5″, or between 0.25″ and 0.45″, or between 0.25″ and0.4″ or between 0.3″ and 0.4″, or between 0.3″ and 0.45″, or between0.35″ and 0.4″. The thickness t of the base of each heat sink may beindependently less than 1″, or less than 0.75″, or less than 0.5″, orless than 0.4″, or less than 0.3″, or less than 0.2″, or less than0.15″, or less than 0.1″, or less than 0.05″, or between 0.05″ and 0.5″,or between 0.075″ and 0.35″, or between 0.1″ and 0.25″, or between 0.1″and 0.2″, or 0.1″, or 0.15″, or 0.2″ . The ratio of center to centerspacing (s) to the fin height (h) (i.e. s/h) may be independently 0.1,0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.5, 0.6, 0.65, 0.7, orbetween 0.1 and 0.7, or between 0.15 and 0.5, or between 0.2 and 0.4, orbetween 0.2 and 0.35, or between 0.25 and 0.3. The dimensions of any finmay be identical or different from the dimensions of any other fin onthe same heat sink. The dimensions of any fin or base may be identicalor different from the dimensions of any other fin on another heat sinks.The dimensions of all heat sink bases on a module may be the same. Thedimensions of all heat sink fins of all heat sinks on a module may bethe same. The dimensions of all heat sink fins of an individual heatsink may be the same. The height of all fins of a heat sink may be thesame. The height of all fins of a heat sink may be different. Theaverage height of all fins of a heat sink may be of any dimensiondescribed above. The average center to center spacing of all fins of aheat sink may be of any dimension described above. The average width ofall fins of a heat sink may be of any dimension described above.

The dimensions of each heat sink may independently be any combination ofthe dimensions described above, such as w between 0.002″ and 0.1″, hbetween 0.75″ and 5″, s between 0.2″ and 0.5″, and t between 0.1″ and0.25″; w between 0.001″ and 0.25″, h between 0.75″ and 5″, s between0.2″ and 0.5″, and t between 0.1″ and 0.25″; w between 0.02″ and 0.05″,h between 0.75″ and 5″, s between 0.2″ and 0.5″, and t between 0.1″ and0.25″; w between 0.002″ and 0.1″, h between 0.25″ and 7″, s between 0.2″and 0.5″, and t between 0.1″ and 0.25″; w between 0.002″ and 0.1″, hbetween 0.9″ and 2″, s between 0.2″ and 0.5″, and t between 0.1″ and0.2″; w between 0.002″ and 0.1″, h between 0.75″ and 5″, s between 0.05″and 1″, and t between 0.1″ and 0.25″; w between 0.002″ and 0.1″, hbetween 0.75″ and 5″, s between 0.3″ and 0.4″, and t between 0.1″ and0.25″; w between 0.002″ and 0.1″, h between 0.75″ and 5″, s between 0.2″and 0.5″, and t between 0.05″ and 0.5″; and w between 0.002″ and 0.1″, hbetween 0.75″ and 5″, s between 0.2″ and 0.5″, and t between 0.1″ and0.2″.

A long axis of fins 210 may be substantially parallel or substantiallyperpendicular to a long axis of the base. Substantially parallel is whentwo referenced axes form an angle of less than 10°. Substantiallyperpendicular is when two referenced axes form an angle between 85° and95°. A long axis is an axis parallel to the longest straight edge of theobject referenced. A long axis is implied if no axis is referenced. Thefins may run continuously along most or all of the length of the base.Fins may form different angles with respect an axis of the heat sink(e.g. a fan orientation), so that air may pass freely through many ofthe channels formed by adjacent fins regardless of wind direction.Surfaces of fins may also have features such as ridges or bumps thathelp induce eddies in air flowing past the fins to help convection.

A heat sink may be designed such that a first volume (defined as avolume of a heat sink including its associated heat sink base) is apercentage of a second volume (defined as a volume from a top-downprojected surface area of the heat sink base and a third dimension,wherein the third dimension is defined by the least squaresdetermination from the heights of each protrusion on the heat sink base(such as cones, fins, etc.)). For example, if all protrusions of a heatsink are of equal dimensions then the first volume would be the heatsink base volume added to the product of the volume of each protrusionand the number of protrusions; and the second volume would be thetop-down projected surface area of the heat sink base (e.g.width×length, if the heat sink base were rectangular) multiplied by theprotrusion height (i.e. the third dimension). If the heights ofprotrusions within a heat sink are different, then the least squaresdetermination of all protrusion heights would determine the thirddimension used in the example above. The percent volume is the firstvolume divided by the second volume×100. The percent volume may be, forexample, between 10% and 50%, between 15% and 45%, between 20% and 40%,between 25% and 35%, between 20% and 30%, between 25% and 30%, between30% and 35%, between 35% and 40%, between 40% and 45%, between 45% and50%, between 20% and 25%, between 15% and 20%, between 10% and 15%,between 10% and 20%, between 15% and 25%, between 25% and 35%, between30% and 40%, between 35% and 45%, between 40% and 50%, between 10% and25%, between 15% and 30%, between 20% and 35%, between 25% and 40%,between 30% and 45%, between 35% and 50%, between 10% and 12.5%, between12.5% and 15%, between 15% and 17.5%, between 17.5% and 20%, between 20%and 22.5%, between 22.5% and 25%, between 25% and 27.5%, between 27.5%and 30%, between 30% and 32.5%, between 32.5% and 35%, between 35% and37.5%, between 37.5% and 40%, between 40% and 42.5%, between 42.5% and45%, between 45% and 47.5%, or between 47.5% and 50%.

FIG. 3 is a top-down view of a heat sink 130 with optionally presentchannels 300 formed by segmented heat sink fins 320. Each channelprovides an additional opening to the interior of the heat sink andallows increased airflow to the internal fins. Channels may be of anypattern, such as general cross-cut, herringbone, or undulating. The finsmay also be replaced with other heat dissipating shapes attached to thebase, such as pyramids (including frustum pyramids), cylinders, squarepegs, or cones (including frustum cones).

The heat sink may be configured to reduce the temperature of aphotovoltaic cell in ambient quiescent air that is at standardtemperature and pressure and an irradiance (E) by white lightindividually or in any combination of 800 W*m⁻², 1000 W*m⁻², or 1200W*m⁻² by at least 1° C.; or by at least 2° C.; or by at least 5° C.; orby at least 7° C.; or by at least 10° C.; or by at least 12° C.; or byat least 15° C.; or by at least 20° C. as compared to an identical celllacking the heat sink. The size, number, and spacing of fins, the sizeof the base portion, and the materials of construction of the heat sinkmay be selected based on the desired decrease in temperature over thecomparative PV cell.

The heat sink may be configured to maintain a photovoltaic cell at atemperature below about 175° F., or below about 160° F., or below about150° F., or below about 140° F., or below about 130° F., or below about120° F., or below about 110° F., or below about 100° F., or below about90° F., or below about 80° F. in quiescent ambient air at a temperatureof 70° F. at standard pressure.

The heat sink may be configured to increase the energy conversionefficiency (defined by the equation: η=(P_(m)/(E×A_(c))), where P_(m) ismaximum electrical power in watts, E is the input light irradiance inW*m⁻² and A_(c) is the surface area of the solar cell in m²) ortotal-area efficiency of a photovoltaic cell (which may be defined bythe relative change in current (I) and/or voltage (V) or relative changein the product of I and V) in ambient quiescent air that is at standardtemperature and pressure and an irradiance (E) by white lightindividually or in any combination of 800 W*m⁻², 1000 W*m⁻², or 1200W*m⁻² by at least 0.5%; or by at least 1%; or by at least 1.5%; or by atleast 2%; or by at least 2.5%; or by at least 3%; or by at least 3.5%;or by at least 4%; or by at least 4.5%; or by at least 5%; or by atleast 5.5%; or by at least 6%; or by at least 6.5%; or by at least 7%;or by at least 7.5%; or by at least 8%; or by at least 8.5%; or by atleast 9%; or by at least 9.5%; or by at least 10% as compared to anidentical cell lacking the heat sink.

If desired, the heat sink may be subjected to forced airflow provided byany means, e.g. one or more fans, to increase airflow over the heat sinkand increase cooling effectiveness of the photovoltaic cell. A fan maydeliver the forced air to the heat sink by direct exposure or remotelythrough a duct system.

The module may contain a protective layer 230 as shown in FIG. 2adjacent to the light-receiving surface of each photovoltaic cell toprotect the photovoltaic cells from damage (caused, for example, frommoisture, dust, chemicals, and temperatures changes), while allowing thetransmission of sunlight. The protective layer may conform to thesurface shape of the photovoltaic cells and may be made of any suitablematerial, such as glass (e.g. low-lead tempered glass) or polymer (e.g.parylene or ethyl-vinyl-acetate). The protective layer may be a film(clear or colored) and be made of e.g. acrylics, epoxies, urethanes, andsilicones. The protective layer may optionally be an antireflectivecoating, such as silicon nitride.

As shown in FIGS. 1 and 2, a photovoltaic module may have a frame 120with mounting fixtures such as screw holes, tabs, and/or electricalconnections that are suitable to mount the module in framework that isattached to a finished roof-top so that heat from the solar cells may bedissipated into ambient air. The frame may surround the photovoltaiccells and, optionally, may surround additional layers that may bepresent adjacent to cells. It is preferable for roof-top mounting thatlittle or none of the frame of the module blocks access to the heatsinks 130 so that relatively cool air may flow freely through thecooling fins. In one experiment, blocking access to the heat sink via aframe resulted in decreased photovoltaic efficiency. FIGS. 1 and 2illustrate how the fins and channels there between are free of the frameso that air may travel through the channels unimpeded by the frame (e.g.allowing horizontal access to the heat sink).

The frame may comprise a flange or lip 102 (straight or curved) as shownin FIG. 1 oriented to direct air flowing through the heat sink upwardupon exiting the module. This feature may prevent hot air generated froma heat sink from entering an adjacent module. Likewise, a flange or lipmay be oriented to force fresh cold air flowing above a module oradjacent module into a heat sink. A feature of this orientation may beparticularly useful to permit cool air to enter the underside of amodule when multiple modules are arranged with minimal interveningspace. Multiple flanges and/or lips may be incorporated into a singleframe to direct cool air into a heat sink and to direct hot air awayfrom a heat sink.

Optionally, legs 140 may be provided to permit the module to be set upona flat surface during handling and prior to installation, thussupporting the weight of the module 100 and preventing compression ofthe fins. Legs 140 may also be used to mount the module to a surfacesuch as a rooftop. Legs may be sufficiently long that they elevate themodule a sufficient distance from the surface to which they are mountedthat air flows freely beneath and through channels through and past thefins to provide improved energy conversion efficiency over a similarconstruction in which the fins touch the surface of the roof top.

The frame 120 and legs 140 may be independently constructed of one ormore materials capable of supporting the photovoltaic module, such asmetal (e.g. aluminum), ceramic, cement, composite, or polymer (e.g.conductive polymer). The frame and heat sink may be constructed as onemold from a conductive polymer, if desired. The frame may have anextended configuration to cover the heat sink wherein the frame may alsoinclude a screen or perforations along the sides to allow air flow tothe heat sinks.

The framework into which modules may be inserted typically has footersespecially adapted to mount to common roofing materials such ascomposite roofing or wood battens forming part of the roof structure.Often, the framework has a height such that fins of the module's heatsink just touch or are just above the surface (e.g. rooftop) on whichthe framework is mounted. Alternatively, the framework may elevate themodule over the rooftop a sufficient distance that air may flowsufficiently freely beneath and through the channels between fins toprovide improved efficiency over a similar construction in which thefins touch the rooftop.

A photovoltaic module may be formed in standard lengths of approximatelye.g. 3 feet, 4 feet, 5 feet, 6 feet, 7 feet, 8 feet, 9 feet, 10 feet, or1 meter, 1.5 meter, 2 meter, 2.5 meter, 3 meter, 3.5 meter, or 4 meter.The photovoltaic module may be formed in standard widths ofapproximately e.g. 1 foot, 1.5 feet, 2 feet, 2.5 feet, 3 feet, 3.5 feet,4 feet, 4.5 feet, 5 feet, or 0.25 meter, 0.5 meter, 0.75 meter, 1 meter,1.25 meter, 1.5 meter, 1.75 meter, or 2 meter.

Photovoltaic modules typically contain 3, 6, 9, 12, 15, 18, 21, 24, 27,30, 20, 24, 28, 32, 36, 40, 25, 36, 45, 50, 42, 48, 54, 60, or 72 PVcells arranged in rows and columns. PV cells may be arranged, forinstance, 4×9, 6×8, 6×9, 6×12, or 8×12. A module may, for example, havefrom five to ten heat sinks in instances where a single heat sink is incontact with cells across an entire row of PV cells in the module.

A typical photovoltaic module may have an overall width of between 35″and 40″, an overall length of between 50″ and 60″, photovoltaic cells ina 6×9 configuration, and 9 heat sinks each spanning a column ofphotovoltaic cells across the width of the module. When viewing thesolar-cell side of the module in which light receiving surfaces of thecells are visible (“top-down”) the width of a module is the minor axisor the shortest distance between opposite walls of the frame. Columnsspan the module width, while rows span the module length. In anotherconfiguration, a photovoltaic module may have an overall width ofbetween 35″ and 40″, an overall length of between 45″ and 55″,photovoltaic cells in a 6×8 configuration, and 8 heat sinks eachspanning a column of photovoltaic cells across the width of the module.In another configuration, a photovoltaic module may have an overallwidth of between 20″ and 30″, an overall length of between 50″ and 60″,photovoltaic cells in a 4×9 configuration, and 8 heat sinks eachspanning a column of photovoltaic cells across the width of the module.In another configuration, a photovoltaic module may have an overallwidth of between 30″ and 40″, an overall length of between 50″ and 55″,photovoltaic cells in an 8×12 configuration, and 12 heat sinks eachspanning a column of photovoltaic cells across the width of the module.Other module configurations described within (such as heat sinksspanning the length of the module) may be applied to the examples above.

In one example, a module was constructed containing 36 photovoltaiccells in a 4×9 configuration of moncrystalline silicon (225 μmthickness). The cells were laminated with glass using an SPI-laminator(Spire, Inc.) and heat sinks attached using omegabond® 101 epoxy cement.Heat sinks contained fins with the following dimensions: w=0.06″,h=0.9375″, s=0.3″, and t=0.1″. Each heat sink contained eight fins andhad an overall width of 2.5″. Two heat sinks were abutted such that theoverall width of the joined heat sinks was 5″ in order to cover thewidth of each photovoltaic cell.

Often anywhere from 4 to 20 modules are installed in a solar module onthe roof-top of a house, depending on the amount of south-facing (in thenorthern hemisphere) rooftop that is available. Many more solar modulesmay be installed on the larger roofs of commercial buildings, forinstance.

The photovoltaic modules described herein may be linked together by anymethod and/or using any apparatus known in the art. Photovoltaic modulesmay also be designed to interlock mechanically and/or electronically, asdescribed in U.S. Provisional Application No. 60/874,313, entitled“Modular Solar Roof Tiles And Solar Panels With Heat Exchange” filedDec. 11, 2006, which is incorporated by reference in its entirety.Modules may also be separated from one another with sufficient space toallow increased airflow between the modules to improve cooling ofphotovoltaic cells.

Another feature of the present invention is a method of manufacturing aphotovoltaic module. FIGS. 4A-4E are different views during thedescribed fabrication process of a photovoltaic module.

FIG. 4A-1 illustrates a cross-sectional view of a system used toconstruct a photovoltaic module. An upper jig 400 comprises anoptionally present depression 410 designed to complement one or morephotovoltaic cells. The depression may have a depth 420 roughly thethickness of the photovoltaic cell(s), or less than the thickness of thecell or cells. Vacuum channels 487 in any shape, number, andconfiguration may be present to allow a vacuum source through the upperjig to the photovoltaic cell(s). A vacuum source may allow thephotovoltaic cells(s) to be temporarily held within the depression 410during the manufacturing process. FIG. 4A-2 shows the upper jig 400 froma bottom view. Each depression 410 is shown with its corresponding width482 and length 484. The width and length can independently have roughlythe same dimensions as the largest surface of the cell or cells, or haveslightly larger dimensions. The number of depressions 410 may be unitedor separated and any number desired for the module, such as 1, 2, 3, 4,5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 25. Theshape of a depression may be of any shape of photovoltaic cell or cells,such as square, rectangular, hexagonal, octagonal, triangular, circular,or diamond.

A lower jig 440 shown in FIG. 4A-1 may comprise a base depression 450and fin depressions 460. The base depression 450 and fin depressions 460may be designed to collectively compliment a heat sink such that theheat sink may be inserted into the lower jig and is incapable ofsubstantial horizontal movement following insertion. The base depressionmay have a depth 470 roughly the thickness of a heat sink base orslightly less than the thickness of a heat sink base, and a widthroughly the same as the heat sink base or slightly larger than the heatsink base. The base depression may be optionally present. Each findepression 460 may have roughly the same dimensions as the heat sinkfins or slightly larger dimensions to allow uninhibited insertion of theheat sink. The lower jig 440 may also be designed to complement anynumber of heat sink designs describe herein, such as pyramids (includingfrustum pyramids), cylinders, square pegs, or cones (including frustumcones). Vacuum channels (not shown) may be present to provide a vacuumsource through the lower jig to the heat sink, as described for theupper jig.

The material of the upper and lower jig may be independently anymaterial known in the art, such as aluminum, copper, ceramic, andpolymer. The upper jig and the lower jig may be in reverse orientation,such that the upper jig is below the lower jig.

The photovoltaic module manufacturing process may begin by placing thephotovoltaic cell(s) and the heat sink into their respective jigs, asillustrated in FIG. 4B. The upper jig 400 houses one or morephotovoltaic cells 486 inserted into each depression 410 such that aflat surface of each cell 488 is exposed while most of the remainingsurface area of each cell is housed within depression. Each cell may bemade of any material described herein or known in the art, such aswafer-based cells formed on a monocrystalline silicon, poly- ormulticrystalline silicon, or ribbon silicon substrate, and may be of anyshape, such as square, rectangular, hexagonal, octagonal, triangular,circular, or diamond. The cell(s) may be temporarily fixed to the upperjig 400 by gravity, vacuum (using e.g. optionally present vacuumchannels 478), or any common adherent. The lower jig 440 houses the heatsink 490 such that a flat surface of the heat sink 492 is exposed whilemost of the remaining surface area, such as the fins, is housed withindepression. The heat sink may be made of any thermally conductivematerial known in the art and/or described herein, such as aluminum oraluminum alloy (e.g. 6063 aluminum alloy, 6061 aluminum alloy, and 6005aluminum alloy), copper, graphite, or conductive polymer (such asconductive elastomer), may be of any color (e.g. blue, black, gray, orbrown) and may comprise cooling surfaces configured of any geometry,such as pyramids (including frustum pyramids), cylinders, square pegs,or cones (including frustum cones). The heat sink may be temporarilyfixed to the lower jig 440 by gravity, vacuum, or any common adherent.

FIG. 4C illustrates how an intervening layer 494 may be added to theexposed surface of the heat sink 492 or to the exposed surface(s) of thecell(s). The intervening layer may be a thermal interface layer, such asthermally conductive grease (e.g. conductive epoxy, silicone, orceramic) or an intervening polymer such as a thermally conductivepolymer. The intervening layer may be of any material commonly used inthe art (e.g. ethyl-vinyl-acetate (EVA), polyester, Tedlar®, EPT). Thethermal interface layer may be, for example, constructed of any materialthat is both electrically isolative and thermally conductive and may bea compound or mixture of compounds that chemically react when exposed toair, heat, and/or pressure. The intervening layer may comprise multiplelayers, such as an electrically isolating layer next to PV cells and athermally conductive layer next to a heat sink, or may be absent. Thelayer may be in simultaneous contact with both the photovoltaic cell(s)and the heat sink.

As illustrated in FIG. 4D, both jigs house the heat sink 490, optionallypresent intervening layer 494, and photovoltaic cell(s) 486 aresandwiched together to allow simultaneous contact of the optionallypresent intervening layer 494 with the heat sink and the photovoltaiccell(s). Sufficient pressure may be applied to either the upper jig 400,lower jig 440, or both, in a direction toward the photovoltaiccomponents to allow pressure between the cell(s) and the heat sink, andforce intimate contact of their surfaces. Because the upper jig iscomplementary to the housed cell(s) 486, the resulting applied pressureis distributed across the area of a cell-upper jig interface, thuspreventing the likelihood of damage to the cell(s). Likewise, becausethe lower jig is complementary to the housed heat sink, the appliedpressure may be less likely to damage the heat sink fins (e.g. crushingor warping the fins). Sufficient heat may also be applied during theprocess, separately or in conjunction with sufficient pressure, tointimately join the heat sink to the photovoltaic cell(s). This processof temporarily applying pressure and/or heat to unite two or morematerials together, also known as laminating, may allow the surface(s)of the cell(s) to more closely contact an adjacent material at amicroscopic level and allow increased conductive heat transfer away fromthe cell(s). A vacuum may be applied to decrease air pressure before,during, and/or after applying pressure and/or heat to aid in removingpockets of air between layers. Removing trapped air may allow a moreintimate contact between layers resulting in increased thermal transfer.

Conditions during lamination may vary depending on the photovoltaicmodule configuration. In one instance the lamination temperature isapproximately 155° C., decreased air pressure is applied for fiveminutes, and one atmosphere of pressure is applied by the jigs to forcethe heat sink and photovoltaic cell(s) between the jigs together forseven minutes. In another instance, the lamination temperature isbetween 100° C. and 200° C., or between 125° C. and 175° C., or between135° C. and 155° C. In another instance 1.25, 1.5, 2, 2.5, 3, 3.5, 4,4.5, or greater than 5 atmospheres of pressure is applied by the jigs toforce the heat sink and photovaltaic cell(s) between the jigs together.In another instance, pressure is applied by the jigs for 1 to 30minutes, 2 to 20 minutes, 5 to 15 minutes, or greater than 30 minutes.In another instance decreased air pressure is applied for 1 to 30minutes, 2 to 20 minutes, 5 to 15 minutes, or greater than 30 minutes.

FIG. 4E illustrates a photovoltaic module following removal of the upperjig and the lower jig.

The process may comprise additional layers known in the art (e.g.ethyl-vinyl-acetate (EVA), polyester, Tedlar®, EPT) on or within themodule, such as a protective layer (e.g. conformal coating), asdescribed herein.

The process may further comprise the addition of a frame, with orwithout legs, as described herein, to permit airflow through directhorizontal access to the heat sinks.

1. A method of fabricating a photovoltaic module comprising the stepsof: placing a heat sink in a jig such that a lower surface of said heatsink is in contact with said jig and an upper surface of said heat sinkis exposed; placing a photovoltaic cell adjacent said upper surface;joining said photovoltaic cell and said heat sink; and removing saidheat sink from said jig.
 2. The method according to claim 1, wherein thestep of joining said photovoltaic cell and said heat sink compriseslaminating.
 3. The method according to claim 2, wherein the step oflaminating comprises providing a thermal interface layer between saidupper surface and said photovoltaic cell.
 4. The method according toclaim 3, wherein the step of laminating comprises laminating the heatsink, intervening layer, and photovoltaic cell together.
 5. The methodaccording to claim 4, wherein said intervening layer is a thermallyconductive polymer.
 6. The method according to claim 5, wherein saidthermally conductive polymer is an elastomer.
 7. The method according toclaim 2, wherein the step of laminating comprising decreasing ambientpressure between said upper surface and said photovoltaic cell.
 8. Themethod according to claim 7, wherein the ambient pressure is decreasedfor between 5 to 30 minutes.
 9. The method according to claim 2, whereinthe step of laminating comprising increasing the temperature betweensaid upper surface and said photovoltaic cell.
 10. The method accordingto claim 9, wherein the temperature is increased to between 125° C. and175° C.
 11. The method according to claim 9, wherein the temperature isincreased for between 5 to 30 minutes.
 12. The method according to claim2, wherein the step of laminating comprises increasing the pressurebetween said upper surface and said photovoltaic cell.
 13. The methodaccording to claim 12, wherein the pressure is increased to between 0.5and 5 atmospheres.
 14. The method according to claim 12, wherein thepressure is increased for between 5 to 30 minutes.
 15. The methodaccording to claim 1, comprising attaching a protective layer on thephotovoltaic cell.
 16. The method according to claim 15, wherein saidprotective layer is a conformal coating.
 17. The method according toclaim 1, comprising attaching a frame surrounding the one or morephotovoltaic cells wherein the frame does not extend beyond said uppersurface, allowing unimpeded access of ambient air to the heat sink. 18.The method according to claim 1, wherein the heat sink is constructed ofextruded aluminum.
 19. The method according to claim 1, wherein the heatsink is constructed of a conductive polymer.
 20. The method according toclaim 1, wherein the heat sink comprises a plurality of fins positionedsubstantially parallel to each other and wherein said jig comprises aplurality of depressions complementary to said plurality of fins.